The present inventions relates to railroad freight cars, and particularly to a well car of light-weight construction, for optionally carrying either intermodal cargo containers stacked one upon another or over-the-highway trailers supported on their own running gear in the well.
Railroad cars for carrying over-the-highway trailers are well known, as are railroad freight cars defining container wells for carrying various combinations of intermodal cargo containers stacked one upon another in two tiers. Because the total weight which can be carried upon the rails limits the net amount of cargo which can be carried on a railroad freight car, it is desirable for a well car to be constructed in a configuration having a minimum tare weight consistent with the strength required to safely support a combination of cargo containers for which the car is configured. It is also necessary, however, to provide an adequate surface to support the tires of trailers carried in the cargo well. Additionally, it is necessary for a car to be strong enough to withstand the many forces resulting from movement of the laden car as part of a train.
It is desired, then, to provide a well car capable of carrying the concentrated stresses resulting from carriage of intermodal cargo containers, while still having a minimum tare weight.
It is also desirable to provide a well floor structure whose vertical height, or overall thickness, is kept small, in order to minimize overall height of the well car when it is laden with containers stacked atop one another.
It is also necessary to provide a shallow well depth from floor top surface to the top of side sill giving trailer loading equipment access to the bottom of a trailer floor above the side sills so that trailers can be inserted into and extracted from the well. The reduction of bending resistance resulting from shallower side sills must be restored by other structure.
Well cars utilize inter box connectors (IBCs) to interconnect upper and lower containers when they are carried stacked one atop another in a well car. IBCs are usually located at a standard position between such stacked containers, corresponding to the location of an end of a standard intermodal container 40 feet long, for example, even though it is possible that a container more than 40 feet long may be carried.
It is necessary for a person to reach the IBC to operate it to interconnect or disconnect containers when a container is being loaded or removed from atop a lower tier container carried in a well of such a car. Since some containers are over 9' high, it may be difficult to reach the IBCs when standing atop a side sill of a container car, particularly one which has relatively low side sills. There is additional risk of falling where a well car is intended to carry containers having lengths greater than 40 feet. Some cars for carrying stacked containers therefore include walkways on which a person can stand to reach IBCs.
Some railroad freight cars are designed to carry trailers, or chassis and attached intermodal cargo containers, in a cargo well also equipped to carry stacked containers. The structure of such well cars must satisfy certain requirements. First, any walkway intended to provide access to IBCs interconnecting stacked containers carried in such a car should be located where they will not interfere with the proper operation of cranes used to move trailers into or out of such cars. Nevertheless, there is a significant likelihood that a loaded trailer or a trailer-loading crane will contact the uppermost part of a side sill or a walkway associated with the top of a side sill of such a well car, because of the need to move a trailer within the cargo well to engage the trailer hitch which is used to secure the trailer to the car.
Second, it is necessary for the car structure to carry loads, imposed upon the car by the weight of containers or trailers, from the side sills to the wheeled trucks supporting the car. However, such loads are concentrated in the side sill structure of the car near the ends, because of the need for clearance for the wheeled trucks to pivot.
Finally, a walkway for providing access to IBCs needs to have a non-skid upper surface, so that a worker can safely stand on the walkway despite wet, snowy, or icy conditions.
Previous attempts to provide the dual capacity for carrying containers or trailers have included cars incorporating transverse beams supporting substantial gratings on which to receive the tires of a trailer carried in the well, as disclosed in Pavlick U.S. Pat. No. 4,456,413. While such cars provide ample strength for carrying both containers and trailers, the structure is undesirably heavy, and the well floor thickness is greater than desired, leaving less than the desired amount of vertical space available for stacked cargo containers. The car disclosed in Gutridge U.S. Pat. No. 3,357,371 has a similar lack of vertical clearance.
Jamrozy U.S. Pat. No. 4,949,646, and Lindauer et al. U.S. Pat. Nos. 4,876,968 and 4,771,706 all disclose a well car for carrying containers, in which a well floor structure includes transverse floor beams. Johnstone et al. U.S. Pat. No. 4,782,762 discloses a well car including a floor with longitudinal and transverse beams, for carrying containers. Cordani U.S. Pat. No. 4,091,742 discloses a well car including a floor structure of transverse and diagonal beams for supporting containers, but none of these patents discloses structure for supporting the wheels of a trailer carried in such a well.
Jamrozy et al. U.S. Pat. Nos. 4,889,055 and 4,862,810 disclose a well car including longitudinal channels, transverse channels, and a longitudinal center plate in a well floor structure, but there is no disclosure of structure available to support the wheels of a trailer in the container well.
Hill U.S. Pat. No. 4,703,699 discloses a lightweight side sill structure for a well car for carrying stacked containers, in which an opening is provided in one of a pair of parallel sheets of material, and a stiffener ring surrounding the opening connects the margins of the opening with the other of the two parallel sheets of material.
Other cars, such as those operated by Canadian National Railroad as its CN679500 "Improved Laser" series cars include heavy gratings supported on the flanges of hat-shaped transverse beams, providing structure of ample strength but greater than desired well floor thickness and weight.
Schuller U.S. Pat. No. 4,718,353 discloses a well car including walkways fixed atop side walls defining a well for receiving a container. The walkways disclosed by Schuller, however, are attached to the car at widely spaced-apart locations, and area subject to being easily damaged or dislodged from the side walls of the car as a result of minor errors during handling of containers.
What is needed, then, is an improved structure for a railroad well car body for optionally carrying either stacked containers or trailers, in which a well floor structure and the connection of such a well floor to other parts of the car provide adequate strength without unnecessary weight and with shallow well depth and small floor thickness, and in which provision is made for a person to safely reach and operate inter-box connectors when containers are stacked in the cargo well.